Dispensing devices for liquid comprising a container and a dispensing assembly mounted on or in an opening of the container are well-known. The dispensing assembly which usually is to be operated by hand comprises a pump having an inlet and an outlet. The inlet is in fluid communication with the interior of the container, for instance via a dip tube, one end of the dip tube being connected to the inlet, the other end being arranged in a bottom portion of the interior of the container. By actuating the pump, liquid is drawn into the pump, and dispensed via the outlet through a dispensing opening. Such dispensing devices are applied for numerous applications, such as soap, shampoo, cleaning liquids, etc.
Next to dispensing devices for the dispensing of liquid, propellant-free foam dispensers are known. State of the art foam dispensing devices comprise an air pump and a liquid pump which can simultaneously be actuated by a common operating button. Upon actuation of the liquid and air pump, by a common actuation device, liquid and air are mixed in a mixing chamber and formed into a foam, which foam is dispensed through a dispensing opening. Such foam dispensing device is for instance disclosed in U.S. Pat. No. 5,271,530 or EP 565 713.
A disadvantage of these known foam dispensers is that for the provision of two separate pumps, a relatively large number of parts is needed, and the construction is rather complex. Furthermore, some difficulties may occur with respect to the sealing of the outlets of both pumps. Also, the air pump, in particular a piston air pump may be sensitive for the presence of water and/or soap.
In GB 821793 another foam dispensing device is disclosed. In this foam dispensing device a single liquid bellows pump is used for the dispensing of foam. In the liquid supply channel, i.e. the liquid path from the liquid held in the container to the inlet of the pump, a chamber is provided. In this chamber an air inlet opening is provided by means of an air conduit connected to the environment outside the foam dispensing device. When the bellows pump is actuated, liquid is drawn out of the container into the pump. This flow of liquid also sucks air out of the air inlet opening in the liquid flow. The liquid and air are mixed to form a foam to be dispensed through the outlet opening of the dispensing device.
Although the foam dispensing device as disclosed in GB 821793 provides a less complex alternative for the known dual pump foam dispensing device, it comprises a number of practical disadvantages with the result that the dispensing device has not been successfully introduced on the market.